JCV is a ubiquitous human virus which is associated with the demyelinating syndrome progressive multifocal leukoencephalopathy and several neural tumors in humans such as medulloblastomas, glioblastomas, neuroblastomas, pineocytomas, and undifferentiated neuroectodermal tumors. Transgenic mice containing JCV genes develop, in addition to hypomyelination of the central nervous system, adrenal neuroblastomas, which metastasize to the pituitary glands and other tissues. JCV exhibits a highly specific host range and tissue tropism. This virus replicates exclusively in glial- origin cells in tissue culture. Several studies have established that the restricted host range of JCV to brain tissue is determined at the level of the viral gene transcription. However, the molecular mechanisms that confer the glial-specific activation of the viral gene expression remain unknown. Recent studies in our laboratory have indicated that the JCV control sequence contains a region, designated the B-domain, which by binding to a 45-kD glial-derived protein stimulates the viral early promoter in vitro. The goal of the research outlined in this proposal is to define the mechanism by which the JCV genome is regulated transcriptionally in a cell-specific manner. The experimental design includes: (1) extensive analysis of the JCV control region by linker scanning mutagenesis across the virus enhancer/promoter (2) purification of the participant glial-derived factors that interact with these regulatory elements to homogeneity and cloning the genes encoding these proteins; (3) identification of structural features of the regulatory proteins, i.e., defining DNA-binding domain and activation regions; (4) examination of the mode of expression of the regulatory proteins during brain development. The information obtained from these experiments should increase our current understanding of cell-type specific gene expression in the central nervous system and provide an initial step in devising strategies to impair JCV replication in the central nervous system.